301B: BIG-IP LTM Specialist: Maintain and TroubleshootDemo

By F5 · Question Mode

QuestionQ108

Identify and Resolve LTM Device Issues

Question Image

Refer to the exhibit.

A company uses a complex client software application that connects to one or more virtual servers (VS) hosted on an LTM device. The client software is having issues. An LTM Specialist is assigned to identify the cause of the problem.

The LTM Specialist has the tcpdump extract and knows that the client software has at least one connection to a VS on port 1990. However, when tcpdump is run on the internal VLAN, port 1990 does not appear in the tcpdump.

Why is there no record of port 1990 in the tcpdump?

  • A The LTM device drops the connection.
  • B Port 1990 is a well-known port, so its use is restricted.
  • C The LTM device performs a Port Address Translation (PAT).
  • D The LTM device performs a Network Address Translation (NAT).
Explanation

The connection’s TCP port numbers are translated between the external and internal sides: the external virtual-server connection uses destination port 1990, while the internal-side flow uses destination port 1989 and a changed client source port. This is Port Address Translation (PAT), which changes transport-layer port numbers; NAT would change IP addresses.

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